I was suggesting you just look at the “config” page in emoncms for emonhub.
If data is being sent to emoncms.org you will see it in the logs.
Despite sending data to emoncms.org (hosted by OEM) you can also log your data locally, but even if you do not, you can still create an emoncms user on your local emonpi and use it for debugging and updating etc.
Sometimes there can be delays at emoncms.org, or if you are experiencing network issues due to having both Ethernet and WiFi connected, emonhub will buffer data until the network is up.
All the graph you have posted shows is that the last recieved data was a while ago (hence the straightline from the last data to the current time). That “missing data” might be buffered in emonhub or it might be buffered in the emoncms.org inputs if traffic is heavy. The emonhub.log should reveal all. That is available within your local emoncms even if you are not storing data locally.